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Thread: Should I buy a DEC Rainbow?

  1. #1
    Join Date
    Dec 2020
    Kingston, WA US

    Default Should I buy a DEC Rainbow?

    Hey everyone,

    First of all, I should state that I've never ran CP/M before. Not even once. Not even on a friend's computer.

    But, I've been feeling kind of bored lately and looking for something new to play with. I got started with 8-bit Commodore computers back in the day, and I feel like I've worked with just about everything that has come along since then, so I thought it might be interesting to go back a little further in time from where I got started, and play with CP/M!

    I realize that I could just run it in an emulator. I also have a Commodore 128DCR that I could run it on (the 128 actually has a Z80 in it just for CP/M compatibility mode), but I figure if I'm going to do it, I should do it right and buy something that was actually designed to run CP/M as it's primary OS.

    Obviously, there are a lot of choices. I'm on a budget though, so I certainly can't afford something exotic like an s100 machine. I see fairly affordably Kaypros often, but I really don't like the small built-in screens.

    Then it hit me that the DEC Rainbow was really mostly a CP/M computer (at least it could run CP/M much better than MS-DOS from what I've read), and the more I've looked into it the more I'm fascinated by it. Apparently it has both a Z80 and an 8086, and a version of CP/M that will automatically run a CP/M binary on the appropriate CPU depending on which it was compiled for? That seems pretty cool. I see them at reasonable prices pretty regularly too, maybe even slightly less than the Kaypros.

    It also seems like there is almost no interest in them. I just did a search for YouTube videos from other retrocomputer hobbyists about them, and basically found only one video. I kind of like that they're somewhat obscure, and thus a bit more of a challenge than just downloading a boot disk and-away-you-go. I actually kind of like the bizarro toaster drives too.

    Plus I'm originally from Massachusetts, and so was DEC, so there's that. lol.

    So what do you all think? Would the Rainbow be a good starter CP/M computer? Anything I should watch out for (I know the monitors are VERY prone to cataracts, anything else?) Is there something else that might better suit me? (i.e. cheap but vintage, and runs CP/M natively.)

  2. #2
    Join Date
    Oct 2016
    Dutchess County, New York, USA


    Don't know how easy it is to find a Rainbow, but you could also look for an Epson QX-10 Z80 (CP/M 2.2) or QX-16 Z80/8088 (CP/M & MS-DOS) if you want something with a decent size monitor. But do buy one that comes with a monitor & keyboard since they are hard to find. I think there's a QX-10's on eBay at the moment for well under $500 US.
    Crazy old guy with a basement full of Pentium 1 laptops and parts

  3. #3
    Join Date
    Mar 2012
    Augusta, Georgia, USA


    Kaypro's are by far the easiest to find, and the monitors are not that small. They are really perfectly clear and large enough to see, even for us old people.

    Other than that, you can get into a Multicomp system very cheap and use whatever monitor you want.

  4. #4
    Join Date
    Feb 2012
    Northern Nevada


    The Kaypro is a better choice in my opinion, as the Rainbow is known for various issues (power supply internal cable failure, VR201 cataracts, etc.) The Rainbow is a pretty unique beast, with a hard drive they made pretty good MS-DOS machines. I had a Rainbow 100+ with 5MB hard drive 20 years ago, but ended up selling it as I wasn't using it.

    Running CP/M on your Commodore would be a good place to start, I've used it more on my Apple //e system with Applicard than any dedicated CP/M machine.

    If you're looking for a Kaypro, we have a couple at ComputerCorps in Carson City, NV, I'd have to make some disks to check them out with.

  5. #5


    I love my Rainbows...

    But the 100B/100+ runs DOS much better than CP/M... The only periph connected to the Z80 is the floppy drive. Everything else requires message passing to the 8088...

    But I can get you disks if you get one

  6. #6


    I'd just run it on the C128, myself. Commodore CP/M Plus isn't too bad.
    I use my C128 because I am an ornery, stubborn, retro grouch. -- Bob Masse
    Various projects and oddities:
    Machine room:


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